package com.example.android.bluetoothlegatt;

import android.util.Base64;
import android.util.Log;

import java.security.MessageDigest;
import java.security.spec.AlgorithmParameterSpec;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

public class AESCrypt {
    private final Cipher cipher;
    private final SecretKeySpec key;
    private AlgorithmParameterSpec spec;


    public AESCrypt(String password) throws Exception
    {
        // hash password with SHA-256 and crop the output to 128-bit for key
        MessageDigest digest = MessageDigest.getInstance("SHA-256");
        digest.update(password.getBytes("UTF-8"));
        byte[] keyBytes = {0x73, 0x68, 0x61, 0x6e, 0x72, 0x65, 0x6e, 0x64,
                0x69, 0x73, 0x63, 0x6f, 0x76, 0x65, 0x72, 0x79};;
        cipher = Cipher.getInstance("AES/CBC/PKCS7Padding");
        key = new SecretKeySpec(keyBytes, "AES");
        spec = getIV();
    }

    public AlgorithmParameterSpec getIV()
    {
        byte[] iv = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, };
        IvParameterSpec ivParameterSpec;
        ivParameterSpec = new IvParameterSpec(iv);

        return ivParameterSpec;
    }

    public byte[] encrypt(byte[] plainText) throws Exception
    {
        cipher.init(Cipher.ENCRYPT_MODE, key, spec);
        byte[] encrypted = cipher.doFinal(plainText);

        Log.w("qob", "encrypted: " + ByteUtil.byte2hex(encrypted));


        return encrypted;
    }

    public String decrypt(String cryptedText) throws Exception
    {
        cipher.init(Cipher.DECRYPT_MODE, key, spec);
        byte[] bytes = Base64.decode(cryptedText, Base64.DEFAULT);
        byte[] decrypted = cipher.doFinal(bytes);
        String decryptedText = new String(decrypted, "UTF-8");

        return decryptedText;
    }
}
